Improved Drilling Assembly Comprising a Friction Bolt

ABSTRACT

A drilling assembly for simultaneously drilling a hole and inserting a friction bolt, the drilling assembly comprising a drill string, a drill bit and a friction bolt, wherein: (i) the drill string defines a leading end adapted to releasably operatively connect to the drill bit and a trailing end adapted to operatively engage with a means for imparting energy on said drill string; (ii) the drill bit is mounted on the leading end of said drill string; (iii) the friction bolt at least partially surrounds said drill string; and wherein (iv) the drilling assembly further comprises an elongate spacer that defines a leading end and a trailing end and is located between said friction bolt and said means for imparting energy on said drill string.

FIELD OF THE INVENTION

The present invention relates to drilling tools and assemblies forinstalling friction bolts and more particularly drill bits for drilltools and assemblies for installing friction bolts. The presentinvention also relates to friction bolts and methods of drillinginvolving friction bolts.

BACKGROUND OF THE INVENTION

Friction bolts are used to stabilise rooves and walls during undergroundmining and most often have a generally cylindrical body and a collar atthe trailing end of the body.

Friction bolts are designed so that when they are driven into a slightlyundersized hole in a formation, such as a rock strata, they resilientlydeform. This resilient deformation exerts radial and frictional forcesagainst the wall of the hole to retain the friction bolt within the holeand to reinforce the rock strata.

Friction bolts can be installed in a two step process where the firststep involves drilling a hole with one drill tool and the second stepinvolves inserting the friction bolt with another tool. This two stepprocess, whilst allowing for the recovery of the entire drill stringused to drill the hole, is time consuming and otherwise inefficient.

The deficiencies with the two step process has lead to the developmentof one step processes where the friction bolt is inserted as the hole isdrilled. A range of drilling tools and assemblies for the one stepprocess have been developed and these tend to rely on the use of drillbits that are detached from the drill string, once the friction bolt hasbeen installed, so the remainder of the drill string can be retrievedthrough the inside of the friction bolt and re-used. The loss of thedrill bit with each friction bolt comes at a cost and also requires anew drill bit to be fitted before the next friction bolt can beinstalled.

The present invention seeks to provide an alternative that at leastpartially addresses one or more of the problems with existing one stepfriction bolt systems.

SUMMARY OF THE INVENTION

According to a first aspect, the present invention provides a drillingassembly for simultaneously drilling a hole and inserting a frictionbolt, the drilling assembly comprising a drill string, a drill bit and afriction bolt, wherein:

-   -   (i) the drill string defines a leading end adapted to releasably        operatively connect to the drill bit and a trailing end adapted        to operatively engage with a means for imparting energy on said        drill string;    -   (ii) the drill bit is mounted on the leading end of said drill        string;    -   (iii) the friction bolt at least partially surrounds said drill        string; and wherein    -   (iv) the drilling assembly further comprises an elongate spacer        that defines a leading end and a trailing end and is located        between said friction bolt and said means for imparting energy        on said drill string.

According a second aspect, the present invention provides a means forimparting energy on a drill string for simultaneously drilling a holeand inserting a friction bolt, said means comprising:

-   -   (i) a drill string adapted to receive the friction bolt thereon,        and    -   (ii) an elongate spacer mounted on said drill string;

wherein said elongate spacer defines a leading end and a trailing endand is adapted to transfer energy from said means for imparting energyon said drill string towards said leading end.

According to a third aspect, the present invention provides a method forsimultaneously drilling a hole and installing a friction bolt into abody requiring reinforcement, the method comprising the steps of:

-   -   (i) providing a drill string including the friction bolt, a        drill bit and an elongate spacer located at the trailing end of        the friction bolt; and    -   (ii) imparting rotational energy to the drill string and impact        energy to the elongate spacer simultaneously.

According to a fourth aspect, the present invention provides a two partdrill bit assembly comprising:

-   -   (i) a first annular drill bit defining a leading end, a trailing        end and an inner surface and comprising a first cutting part        disposed at the leading end;    -   (ii) a second drill bit defining a leading end, a trailing end        and an outer surface and comprising a second cutting part        disposed at its leading end;        wherein the first annular drill bit is adapted to be releasibly        received on the second drill bit via said inner surface of the        first drill bit and said outer surface of the second drill bit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an exploded perspective view of a drilling assembly accordingto one embodiment of a first aspect of the present invention including atwo part drill bit;

FIG. 1B is a perspective side view of the drilling assembly in FIG. 1Ain a ready to drill configuration;

FIG. 1C is a cross sectional side view of the drilling assembly in FIGS.1A and 1B partway through the process of installing a friction bolt;

FIG. 1D is the same view as FIG. 1C but shows the friction bolt fullyinstalled;

FIG. 2A is a perspective view of an example of the elongate spacer thatforms part of the embodiment in FIGS. 1A-1D;

FIG. 2B is cross sectional side view of the elongate spacer in FIG. 2A;

FIG. 3A is a perspective view of an example of the coupling that thatforms part of the embodiment in FIGS. 1A-1D;

FIG. 3B is a perspective view of the coupling in FIG. 3A from theopposite end; and

FIG. 3C is cross sectional side view of the coupling in FIGS. 3A and 3B;

FIGS. 4A to 4C are perspective views of an example of a two part drillbit according to a fourth aspect of the present invention that formspart of the embodiment in FIGS. 1A-1D, where FIG. 4A depicts, thesacrificial part of the bit, FIG. 4B the other part of the bit that isreusable and FIG. 4C the two parts assembled together.

DETAILED DESCRIPTION OF THE INVENTION

According a first aspect of the present invention there is provided adrilling assembly for simultaneously drilling a hole and inserting afriction bolt, the drilling assembly comprising a drill string, a drillbit and a friction bolt, wherein:

-   -   (i) the drill string defines a leading end adapted to releasably        operatively connect to the drill bit and a trailing end adapted        to operatively engage with a means for imparting energy on said        drill string;    -   (ii) the drill bit is mounted on the leading end of said drill        string;    -   (iii) the friction bolt at least partially surrounds said drill        string; and wherein    -   (iv) the drilling assembly further comprises an elongate spacer        that defines a leading end and a trailing end and is located        between said friction bolt and said means for imparting energy        on said drill string.

The present invention is based on the discovery and/or recognition oftwo problems associated with one step or single pass drilling assembliesand their use.

Firstly, operation of prior art systems can result in undesirablerotation of or against the friction bolt during the installationprocess. Such rotation can damage the friction bolt, particularly thetrailing end of the friction bolt. Furthermore, rotation of or againstthe friction bolt reduces the efficiency of the process as therotational energy is better focussed on the drill bit.

Secondly, it is common in prior art systems to experience an increasedfrequency of drill rod breakage during the installation process. Suchbreakages are contributed to by the limited ability of the drillassembly to flex, particularly at the coupling between the drill stringand the drill rig. The flex, particularly at this coupling becomes morelimited as the friction bolt is installed further in the hole.

Surprisingly, applicant has found that the inclusion of an elongatespacer addresses the above problems or at least partially amelioratesthe problems with the prior art.

Preferably, the elongate spacer at least partially surrounds a part ofthe drill string.

Preferably, the part of the drill string is the trailing part of thedrill string.

Preferably, the part of the drill string is the part of the drill stringadjacent to the means for imparting energy on said drilling string,

Preferably, the leading end of the elongate spacer is adapted to contactthe trailing end of the friction bolt and transfer energy from the meansfor imparting energy on said drill string to the friction bolt.

Preferably, the energy transferred from the means for imparting energyon said drill string to the friction bolt is impact energy.

Preferably, the elongate spacer is adapted not to transfer at least someof the rotational energy from the means for imparting energy on saiddrill string to the friction bolt.

Preferably, the elongate spacer is generally cylindrical.

Preferably, the elongate spacer comprises a longitudinal axial passageor bore adapted to receive the drill string therethrough.

Preferably, the longitudinal axial passage or bore defines asubstantially smooth inner surface.

Preferably, the longitudinal axial passage or bore has a uniform crosssectional shape and size.

Preferably, the longitudinal axial passage or bore is sized to enablethe drill string to rotate therein without unduly impacting the elongatespacer.

Preferably, the elongate spacer is at least 50, 100, 150, 200, 300, 400,500, 750 or 1000 mm long.

The drilling assembly may further comprise at least one washer memberlocated between the elongate spacer and the means for imparting energyon said drill string.

Preferably, the washer member at least partially surrounds a part of thedrill string.

Preferably, the washer member at least partially surrounds a trailingpart of the drill string.

Preferably, the washer member at least partially surrounds the part ofthe drill string adjacent to the means for imparting energy on saiddrilling string.

Preferably, the leading end of the washer member is adapted to contactthe trailing end of the elongate spacer and transfer energy from themeans for imparting energy on said drill string to the elongate spacer.

Preferably, the energy transferred from the means for imparting energyon said drill string to the elongate spacer is impact energy.

Preferably, the washer member is adapted not to transfer at least someof the rotational energy from the means for imparting energy on saiddrill string to the elongate spacer.

Preferably, the washer member is a split washer.

Preferably the washer member is an annular ring.

Preferably, the washer member comprises an annulus adapted to receivethe drill string therethrough.

Preferably, the washer member is sized to enable the drill string torotate therein without unduly impacting the washer member.

Preferably, the washer member is at least 10, 20 or 30 mm long.

Preferably, the at least one washer member comprises two washer members.

Preferably, the at least one washer member is lubricated.

The drilling assembly may further comprise a coupling member adapted tooperatively connect the means for imparting energy on said drill stringwith the drill string.

Preferably, the coupling member is adapted to releasably couple themeans for imparting energy on said drill string with the drill string.

Preferably, the coupling member is generally cylindrical and definesfirst and second threads.

Preferably, the first and second threads are located at opposed ends ofthe coupling member

Preferably the first and second threads have different widths. In thisregard, it is preferred that the coupling member is a reducer.

Preferably, the first thread on the coupling member is adapted to engagewith a suitably threaded portion on the trailing end of the drill stringand the second thread of the coupling member is adapted to engage with asuitably threaded portion on the means for imparting energy.

Preferably, the drill bit is disposable.

Preferably, the drill bit comprises a plurality of parts. When the drillbit comprises two parts it is preferred that one part is disposable andthe other part is reusable.

Preferably, the disposable drill bit or drill bit part is adapted to bedetached from the drill string or other part of the drill bit prior toretraction of the drill string from the hole at the end of the drillingprocess.

Preferably, the drill bit is adapted to be releasibly engaged with theend of the friction bolt. In this regard, the drill bit may comprise ameans for engaging with end of friction bolt. Preferably, the means forengaging with end of friction bolt is a circumferential groove on thedrill bit that provides for a friction fit between the friction bolt andthe drill bit.

Preferably, the friction bolt is a generally cylindrical structureadapted to be inserted into a rock or other formation to providereinforcement. Preferably, the friction bolt is adapted to exert outwardpressure on the hole into which it has been inserted. Preferably, thefriction bolt has a configuration when inserted into a formation or insitu (“stressed configuration”) where the width or diameter of thelongitudinal axial passage therein is reduced relative to the width ordiameter of the longitudinal axial passage prior to insertion of thefriction bolt (“relaxed configuration”).

Preferably, the friction bolt defines a longitudinal axial passage.

Preferably, the friction bolt comprises a longitudinal split along atleast a portion of its length and whereby radial expansion of the tubeis facilitated by lateral expansion of the longitudinal split.Preferably, the longitudinal split extends the full length of thefriction bolt.

Instead of a longitudinal split, the friction bolt may comprise a foldor overlap extending along at least a portion of its length that enablesthe friction bolt to exert outward pressure on the hole into which it isinserted. In this regard, the fold or overlap is adapted to function asa spring that when constrained in the drill hole exerts outward pressureon the hole.

According a second aspect of the present invention there is provided ameans for imparting energy on a drill string for simultaneously drillinga hole and inserting a friction bolt, said means comprising:

-   -   (i) a drill string adapted to receive the friction bolt thereon,        and    -   (ii) an elongate spacer mounted on said drill string;        wherein said elongate spacer defines a leading end and a        trailing end and is adapted to transfer energy from said means        for imparting energy on said drill string towards said leading        end.

Preferably the means for imparting energy on a drill string is adrilling machine such as a jumbo.

According to a third aspect of the present invention there is provided amethod for simultaneously drilling a hole and installing a friction boltinto a body requiring reinforcement, the method comprising the steps of:

-   -   (i) providing a drill string including the friction bolt, a        drill bit and an elongate spacer located at the trailing end of        the friction bolt; and    -   (ii) imparting rotational energy to the drill string and impact        energy to the elongate spacer simultaneously.

Preferably, the method further comprises the step of not applyingrotational energy to the elongate spacer and/or the friction bolt.

Preferably, the method further comprises the step of not rotating theelongate spacer and/or the friction bolt.

Preferably, the method further comprises the step of detaching at leastpart of the drill bit prior to retracting the drill string from thehole.

According to a fourth aspect of the present invention there is provideda two part drill bit assembly comprising:

-   -   (i) a first annular drill bit defining a leading end, a trailing        end and an inner surface and comprising a first cutting part        disposed at the leading end;    -   (ii) a second drill bit defining a leading end, a trailing end        and an outer surface and comprising a second cutting part        disposed at its leading end;        wherein the first annular drill bit is adapted to be releasibly        received on the second drill bit via said inner surface of the        first drill bit and said outer surface of the second drill bit.

Preferably, the inner surface of the first annular drill bit defines aplurality of recessed portions and the outer surface of the second drillbit defines a plurality of raised portions that are compatibly shaped.

Preferably, the second drill bit further comprises a shank member at itsfollowing end adapted to operably engage with a drill string.

Preferably, the first annular drill bit comprises a drill bit accordingto FIG. 4A.

Preferably, the second drill bit comprises a drill bit according to FIG.4B.

Preferably, the two part drill bit comprises a drill bit according toFIG. 4C.

General

Those skilled in the art will appreciate that the invention describedherein is susceptible to variations and modifications other than thosespecifically described. The invention includes all such variation andmodifications. The invention also includes all of the steps and featuresreferred to or indicated in the specification, individually orcollectively and any and all combinations or any two or more of thesteps or features.

Each document, reference, patent application or patent cited in thistext is expressly incorporated herein in their entirety by reference,which means that it should be read and considered by the reader as partof this text. That the document, reference, patent application or patentcited in this text is not repeated in this text is merely for reasons ofconciseness. None of the cited material or the information contained inthat material should, however be understood to be common generalknowledge.

The present invention is not to be limited in scope by any of thespecific embodiments described herein. These embodiments are intendedfor the purpose of exemplification only. Functionally equivalentproducts and methods are clearly within the scope of the invention asdescribed herein.

The invention described herein may include one or more range of values(e.g. size etc). A range of values will be understood to include allvalues within the range, including the values defining the range, andvalues adjacent to the range which lead to the same or substantially thesame outcome as the values immediately adjacent to that value whichdefines the boundary to the range.

For the purposes of the present invention the terms “leading” and“following” for example in the phrases “leading end” and “following end”refer to positions relative to the drilling process. “Leading” as usedherein refers to a feature or part thereof that is closest or proximalto the drilling interface whereas “following” refers to a feature orpart thereof that is furthest or distal to the drilling interface.

For the purposes of the present invention it is preferred that the term“friction bolt” is interpreted to cover any apparatus adapted to beinserted into a rock or other formation to provide reinforcement byexerting outward pressure on the hole into which it has been inserted.

Throughout this specification, unless the context requires otherwise,the word “comprise” or variations such as “comprises” or “comprising”,will be understood to imply the inclusion of a stated integer or groupof integers but not the exclusion of any other integer or group ofintegers.

Other definitions for selected terms used herein may be found within thedetailed description of the invention and apply throughout. Unlessotherwise defined, all technical terms used herein have the same meaningas commonly understood to one of ordinary skill in the art to which theinvention belongs.

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

Description of the Preferred Embodiments

One embodiment of a drilling assembly, for simultaneously drilling ahole and inserting a friction bolt, according to a first aspect of thepresent invention, is depicted in FIGS. 1A-1D and generally indicated bythe numeral 10. The drilling assembly 10 comprises a friction bolt 12that includes a longitudinal split and is supported on a drill stringincluding a drill rod 14. The drilling assembly also includes a plate 15that is threaded over the friction bolt 12 and provides an increasedsurface area that facilitates the engagement of the flange 17 attrailing end of the friction bolt 12 with mesh (not shown) when thefriction bolt 12 is fully installed.

The leading end of the drill rod 14 includes a threaded portion 16 thatis adapted to engage with a two part drill bit assembly, according to anembodiment of a fourth aspect of the present invention and depictedseparately in FIGS. 4A-4C, via a threaded bore in the shank portion 18of a second drill bit in the form of reusable drill bit 20. The otherpart of the two part drill bit assembly comprises a first annular drillbit in the form of sacrificial drill bit 22 that includes an innersurface shaped to releasibly engage with a suitably shaped outer surfaceon the leading end of the reusable drill bit 20.

The trailing end of the drill rod 14 includes another threaded portion24 that is adapted to operatively engage with a means for impartingenergy on said drill string via a coupling member in the form of acylindrical threaded reducer coupling 26. The reducer coupling includesa first thread 28 and a second thread 30 (best seen in FIG. 3C). Thefirst thread 28 is wider and is adapted to engage with a compatiblethread in the a means for imparting energy on said drill string such asa jumbo (not shown), the second thread 30 is adapted to engage with thethreaded portion 24 on the trailing end of the drill rod 14.

Also supported on the drill rod 14 is an elongate spacer in the form ofgenerally cylindrical spacer member 32 (depicted separately in FIGS. 2Aand 2B) that defines a longitudinal axial passage 34 (best seen in FIG.2B). The longitudinal axial passage 34 is sized to allow for the drillrod 14 to pass therethrough and rotate therein without unduly impactingthe cylindrical spacer member. Between the cylindrical spacer member 32and the reducer coupling 26 is provided a washer member in the form ofring washer 36.

In use, best depicted in FIGS. 1C-1D, the drill assembly 10simultaneously drills a hole and installs a friction bolt 12 into a body38 requiring reinforcement as follows.

A drill rod 14 is operatively connected to a drill rig (not shown) viacylindrical threaded reducer coupling 26. The ring washer 36 andcylindrical spacer member 32 are then placed on to the drill rod 14followed by friction bolt 12 and plate 15. At this stage, the two partdrill bit 20, 22 is then attached to the leading end of the drill rod 14to form the drill string in a ready to use configuration. The operatorthen positions the leading end of the drill string in contact with thebody 38 and commences the drilling process by imparting impact androtational energy on the drill string. In particular, rotational energyis imparted on drill rod 14 that in turn rotates two part drill bit 20,22 to create a hole and impact energy is imparted through reducercoupling 26 and ring washer 36 onto cylindrical spacer member 32 and inturn onto the trailing end of the friction bolt 12. Thus, as the hole isdrilled into body 38, friction bolt 12 is installed therein. Throughoutthe drilling process, debris can be removed by the action of a flushingfluid, such as water and/or air, conveyed through a longitudinal conduitor bore 35 in the drill string that is in fluid communication with theleading end of the part of the drill bit 20 via holes 37 in the part 20of the two part drill bit. Holes 37 extend to the drilling interfacewith the body 38 when the two part drill bit 20, 22 is assembled, viaopenings 40.

The ring washer 36 and cylindrical spacer member 32 act to limit andpreferably prevent rotational energy from the drill rig beingtransferred to the friction bolt 12 during installation. The presentinvention has also been found to limit and preferably preventundesirable breakage of drill rod 14 during the installation of thefriction bolt 12. In this regard, cylindrical spacer member 32preferably ensures that the coupling between the drill rod 14 and thedrill rig is always spaced apart from the body 38 requiringreinforcement. This allows for increased flex of the drill string at allstages of the installation process.

1-54. (canceled)
 55. A drilling assembly for simultaneously drilling ahole and inserting a friction bolt, the drilling assembly comprising adrill string, a drill bit and a friction bolt, wherein: (i) the drillstring defines a leading end adapted to releasably operatively connectto the drill bit and a trailing end adapted to operatively engage with ameans for imparting energy on said drill string; (ii) the drill bit ismounted on the leading end of said drill string; (iii) the friction boltat least partially surrounds said drill string; and wherein (iv) thedrilling assembly further comprises an elongate spacer, located betweensaid friction bolt and said means for imparting energy on said drillstring, that defines a leading end and a trailing end and a longitudinalaxial passage therebetween for receiving the drill string therethroughwithout transferring at least some rotational energy, from said meansfor imparting energy, to the friction bolt.
 56. A drilling assemblyaccording to claim 55, wherein the elongate spacer is adapted to contactthe trailing end of the friction bolt and transfer impact energy fromthe means for imparting energy on said drill string to the frictionbolt.
 57. A drilling assembly according to claim 55, wherein theelongate spacer is generally cylindrical.
 58. A drilling assemblyaccording to claim 55, wherein the longitudinal axial passage defines asubstantially smooth inner surface.
 59. A drilling assembly according toclaim 55, wherein the longitudinal axial passage or bore has a uniformcross-sectional shape and size.
 60. A drilling assembly according toclaim 55, wherein the longitudinal axial passage or bore is sized toenable the drill string to rotate therein without unduly impacting theelongate spacer.
 61. A drilling assembly according to claim 55, furthercomprising at least one washer member located between the elongatespacer and the means for imparting energy on said drill string tocontact the trailing end of the elongate spacer and transfer impactenergy from the means for imparting energy on said drill string to theelongate spacer.
 62. A drilling assembly according to claim 61, whereinthe at least one washer member comprises two washer members.
 63. Adrilling assembly according to claim 55, further comprising a couplingmember adapted to operatively connect the means for imparting energy onsaid drill string with the drill string.
 64. A drilling assemblyaccording to claim 63, wherein the coupling member is generallycylindrical and defines first and second threads.
 65. A drillingassembly according to claim 64, wherein the first and second threads arelocated at opposed ends of the coupling member and the first and secondthreads have different widths.
 66. A drilling assembly according toclaim 63, wherein the coupling member is a reducer.
 67. A drillingassembly according to claim 55, wherein the drill bit comprises aplurality of parts.
 68. A drilling assembly according to claim 67,wherein the drill bit comprises a means for engaging with the end of thefriction bolt.
 69. A drilling assembly according to claim 68, whereinthe means for engaging with end of friction bolt is a circumferentialgroove on the drill bit that provides for a friction fit between thefriction bolt and the drill bit.
 70. A drilling assembly according toclaim 55, wherein the friction bolt is a generally cylindrical structureadapted to be inserted into a rock or other formation to providereinforcement.
 71. A means for imparting energy on a drill string forsimultaneously drilling a hole and inserting a friction bolt, said meanscomprising: (i) a drill string adapted to receive the friction boltthereon, and (ii) an elongate spacer mounted on said drill string andlocated between said friction bolt and said means for imparting energyon said drill string that defines a leading end and a trailing end and alongitudinal axial passage therebetween for receiving the drill stringtherethrough without transferring at least some rotational energy fromthe means for imparting energy on said drill string to the frictionbolt.
 72. A method for simultaneously drilling a hole with a drillstring and installing a friction bolt into a body requiringreinforcement with a means for imparting energy on said drill string andsaid friction bolt, the method comprising the steps of: (i) providingthe drill string including the friction bolt, a drill bit and anelongate spacer located between said friction bolt and said means forimparting energy that defines a leading end and a trailing end and alongitudinal axial passage therebetween for receiving the drill stringtherethrough without transferring at least some rotational energy fromthe means for imparting energy on said drill string to the frictionbolt; and (ii) imparting rotational energy to the drill string andimpact energy to the elongate spacer simultaneously.
 73. A methodaccording to claim 72, further comprising the step of not applyingrotational energy to the elongate spacer and/or the friction bolt.
 74. Amethod according to claim 72, further comprising the step of detachingat least part of the drill bit prior to retracting the drill string fromthe hole.